1. Field of the Invention
The invention relates to a dielectric barrier discharge lamp in which a dielectric barrier discharge forms xe2x80x9cexcimerxe2x80x9d molecules and in which light is used which is emitted by these xe2x80x9cexcimerxe2x80x9d molecules. The invention furthermore relates to an irradiation device in which this dielectric barrier discharge lamp is used as a light source. The invention relates especially to silica glass as the translucent part of a dielectric barrier discharge lamp or a window component of an irradiation device.
2. Description of Related Art
A radiator, i.e., a dielectric barrier discharge lamp in which a discharge vessel is filled with a gas which forms excimer molecules and in which light is emitted which has been radiated by a dielectric barrier discharge of the excimer molecules, is known generally, for example, from the Japanese patent disclosure document HEI 1-144560 or U.S. Pat. No. 4,837,484.
This dielectric barrier discharge lamp is also called an ozone production discharge or a silent discharge, as is described in the xe2x80x9cDischarge Handbook,xe2x80x9d Electroassociation, June 1989, 7th edition, page 263, Japan.
In the aforementioned publications, it is described that a discharge vessel with a roughly cylindrical shape acts at least partially as a dielectric of the dielectric barrier discharge and is translucent, and in it the light is emitted by excimer molecules. Furthermore, it is disclosed herein that silica glass is to be used as the dielectric for passage of light.
One such dielectric barrier discharge lamp has advantages which neither a conventional low pressure mercury lamp, nor a conventional high pressure arc discharge lamp has, such as, for example, emission of UV radiation with a short main wavelength of 172 nm, and at the same time, selective generation of light with individual wavelengths which are somewhat like line spectra, with high efficiency. Furthermore, there is the advantage that a commercial dielectric barrier discharge lamp can be used and it can also be produced easily if silica glass is used as the dielectric and light passage window, as was described above.
It is known that damage by the emitted UV radiation can be reduced when this silica glass contains a suitable number of OH radicals (hydroxyl group), as if the silica glass consists of pure silicon dioxide (SiO2).
Therefore, it is more advantageous if the silica glass contains OH radicals. If the content thereof becomes too great, however, there is the disadvantage that, as a result of absorption of the UV radiation by the OH radicals themselves, the desired amount of radiation soon can no longer be obtained. Conversely, in the case that the content of OH radicals is too low, damage by UV radiation occurs; this causes degradation of the silica glass or similar problems.
Therefore, a primary object of the present invention is to devise a dielectric barrier discharge lamp with a translucent part made of silica glass which contains OH radicals.
A further object of the invention is to devise an irradiation device in which a dielectric barrier discharge lamp is used as the light source and the silica glass which contains OH radicals is used as the window component.
Another object of the invention is, thus, to advantageously suppress damage of the silica glass by UV radiation and to obtain a sufficient amount of UV radiation.
In a dielectric barrier discharge lamp in which a silica glass discharge vessel is filled with a discharge gas which forms excimer molecules by a dielectric barrier discharge and in which this discharge vessel is at least partially provided with a translucent part, the above objects are achieved in accordance with the invention in that, in this translucent part, the ratio of the non-hydrogen bonding OH radicals to the total number of OH radicals is less than or equal to 0.36.
The stated objects are, furthermore, achieved according to the invention in an irradiation device with at least one dielectric barrier discharge lamp and a window component in that the window component is made of silica glass, and in the window component, the ratio of the non-hydrogen bonding OH radicals to the total number of OH radicals is at most equal to 0.36, in which in at least one dielectric barrier discharge lamp in the discharge vessel excimers are produced and UV radiation is emitted by a dielectric barrier discharge, and in which the window component and at least one dielectric barrier discharge lamp are arranged such that the UV radiation of at least one dielectric barrier discharge lamp emerges from the window component.
In the following, the invention is specifically described using one embodiment shown in the drawings.